Control of emissions from fossil fuel combustions sources addresses a major environmental problem. The Environmental Protection Agency (EPA) through the Clean Air Act regulates the emissions from fossil-fuel-fired power plants. Initial regulations were focused on oxides-of-nitrogen (NOx) and oxides-of-sulfur (SOx) emissions, but newer regulations will include provisions to control heavy metals (Hg, etc.) and carbon dioxide. In particular, elemental mercury emissions from coal-fired power plants are a major concern.
Processes are known to remove particulate and oxidized mercury from waste streams. Particulate matter traps some oxidized and elemental mercury and these forms of mercury associated with this particulate matter are removed when the particulate matter is removed. For example, electrostatic precipitators or fabric filters can be used to remove particulate matter from flue gas. Oxidized mercury has varying solubility and can be captured in wet or dry scrubbers, but the results from flue gas desulfurization units are inconsistent. Elemental mercury in flue gas presents a particular challenge in that it is not soluble and must be oxidized before it can be captured in a scrubber system.
For the reasons stated above, and for other reasons stated below that will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for alternative methods and apparatus for treating combustion gas streams.